Methods and systems for imaging and cutting semiconductor wafers and other semiconductor workpieces

ABSTRACT

Methods and systems for imaging and cutting semiconductor wafers and other microelectronic device substrates are disclosed herein. In one embodiment, a system for singulating microelectronic devices from a substrate includes an X-ray imaging system having an X-ray source spaced apart from an X-ray detector. The X-ray source can emit a beam of X-rays through the substrate and onto the X-ray detector, and X-ray detector can generate an X-ray image of at least a portion of the substrate. A method in accordance with another embodiment includes detecting spacing information for irregularly spaced dies of a semiconductor workpiece. The method can further include automatically controlling a process for singulating the dies of the semiconductor workpiece, based at least in part on the spacing information. For example, individual dies can be singulated from a workpiece via non-straight line cuts and/or multiple cutter passes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/765,354filed Jun. 19, 2007, now U.S. Pat. No. 8,053,279, which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The following disclosure relates generally to the manufacture ofmicroelectronic devices and, more particularly, to methods and systemsfor imaging and cutting semiconductor workpieces.

BACKGROUND

Packaged microelectronic devices are used in cellular phones, pagers,personal digital assistants, computers, and many other electronicproducts. Die-level packaged microelectronic devices typically include adie, an interposer substrate or leadframe attached to the die, and amolded casing around the die. The die generally has an integratedcircuit and a plurality of bond-pads coupled to the integrated circuit.The bond-pads can be coupled to terminals on the interposer substrate orleadframe. The interposer substrate can also include ball-pads coupledto the terminals by conductive traces in a dielectric material. Aplurality of solder balls can be attached to corresponding ball-pads toconstruct a “ball-grid” array. The steps for making die-level packagedmicroelectronic devices typically include (a) forming a plurality ofdies on a semiconductor wafer, (b) cutting the wafer to singulate thedies, (c) attaching individual dies to corresponding interposersubstrates, (d) wire-bonding the bond-pads to the terminals of theinterposer substrate, and (e) encapsulating the dies with a moldingcompound.

Another process for packaging microelectronic devices is wafer-levelpackaging. In wafer-level packaging, a plurality of microelectronic diesare formed on a wafer and a redistribution layer is formed over thedies. The redistribution layer includes a dielectric layer, a pluralityof ball-pad arrays on the dielectric layer, and a plurality of tracescoupled to individual ball-pads of the ball-pad arrays. Each ball-padarray is arranged over a corresponding microelectronic die, and thetraces couple the ball-pads in each array to corresponding bond-pads onthe die. After forming the redistribution layer on the wafer, astenciling machine can deposit discrete blocks of solder paste onto theball-pads of the redistribution layer. The solder paste is then reflowedto form solder balls or solder bumps on the ball-pads. After forming thesolder balls on the ball-pads, the wafer is cut to singulate the dies.

Another type of packaged microelectronic device is a build-up package(“BUP”) microelectronic device. BUP devices are formed by placingmultiple singulated microelectronic dies active side down on a temporarycarrier. A fill material is then used to cover the dies and the carrier.Once the fill material cures, the temporary carrier is removed. Theactive sides of the dies are cleaned, and then a redistribution layer isapplied to the active sides. Solder balls can be connected to theredistribution layer, and a dielectric layer can be applied overportions of the redistribution layer so that the solder balls extendthrough the dielectric layer. The fill material between the dies is thencut to separate the dies from one another and form multiple BUP devices.The solder balls and redistribution layer can then be used to connectthe BUP device to a printed circuit board.

BUP devices can also be formed by placing multiple singulated diesactive side down on a temporary carrier, and placing fill materialbetween the dies. Once the fill material hardens, the temporary carrieris removed and the BUP devices are separated by cutting the fillmaterial between the dies. It may be difficult to place a redistributionlayer on the active sides of the dies with this process, however,because the active sides and the fill material may not form asufficiently planar surface for effective application of aredistribution layer, and the dies may be skewed such that precise waferlevel processes cannot be used.

Whether the dies are encapsulated before or after dicing, the dies aregenerally organized in a rectilinear array of rows and columns that areseparated by streets. The rows and columns are spaced apart from eachother in a repeated pattern, generally with a fixed row spacing betweenneighboring rows, and a fixed column spacing between neighboringcolumns. The pattern is generally fixed for a given type of wafer anddie configuration. Accordingly, even if a particular type of wafer hasdies of different sizes, the dies are arranged in a predictable patternthat is repeated from one wafer to the next.

Prior to dicing, a camera or other type of imaging system is used todetect the rotational orientation of the array and the starting point atwhich the dicing process begins. A dicing blade is then brought intocontact with the wafer and either the blade or the wafer is translatedto make the first cut (e.g., along a column). The blade or the wafer isthen stepped over to the next column by a known distance correspondingto the spacing between columns, and the next cut is made. This processis repeated until all the necessary column cuts are completed. At thatpoint, the wafer (or the blade) is rotated 90° and the same process isrepeated until all the row cuts are complete.

While the foregoing process has proven effective for many applications,in certain applications, the spacing between dies may not be consistentfrom one wafer to the next, or within a given wafer. In such a case, therotating blade typically cannot account for spacing variations and as aresult, may cut through dies that would otherwise be suitable forinstallation in an end product. Accordingly, there is a desire toimprove the versatility of current singulation processes.

FIG. 1 is a schematic diagram of a prior art system 100 for imaging asemiconductor wafer 102 (“wafer 102”) and cutting the wafer 102 intoindividual dies. The system 100 includes an infrared camera 110 havingan infrared detector array (not shown). The infrared camera 110 isoperably coupled to a dicing machine 114 via a computer 112. The dicingmachine 114 can include a saw having, for example, a diamond-tippedblade 116 that rotates about a spindle to cut through the wafer 102. Thewafer 102 is supported by a chuck 104 that is operably coupled to a heatsource 106. To facilitate cutting and/or imaging, the chuck 104 is ableto move laterally in an X direction and rotate about its axis in a θdirection. Similarly, the dicing machine 114 is able to move up and downin a Y direction as well as back and forth in a Z direction.

In operation, the heat source 106 heats the wafer 102 to a predeterminedtemperature, causing the wafer 102 to generate infrared photons or“flux.” The detector array in the infrared camera 110 creates a map ofthe wafer 102 based on the flux intensity received by each of theindividual detectors in the array. The computer 112 converts the fluxdetected by each of the detectors into a temperature readingcorresponding to a feature on the wafer 102. This enables the computer112 to determine the location of scribe lines and/or other alignmentfeatures (i.e., fiducials) on the wafer 102. The computer 112 providesthis information to the dicing machine 114, which then cuts the wafer102 along the scribe lines to singulate the individual dies.

Another type of infrared imaging system commonly used to alignsemiconductor wafers does not use a heat source to heat the wafer. Thistype of system is a reflective system that directs infrared radiationdown onto the wafer, and then captures the infrared radiation thatreflects off of the wafer with a camera that generates an image of thewafer.

Many semiconductor wafers include layers of material that can inhibitinfrared imaging. For example, various types of memory and imagingsemiconductor devices include metallized layers on the back side toenhance protection from electromagnetic interference (EMI). Thesemetallized layers can obscure infrared radiation, making accurateinfrared imaging difficult, if not impossible. In addition, when cuttingBUP devices, the mold material can also obscure infrared imaging, againmaking it difficult to accurately detect the location of scribe linesand other alignment features. To overcome these problems, semiconductorwafers can be manufactured so that the metallized layer or mold compoundis prevented from covering the alignment features. Alternatively, theinfrared inhibiting material can be removed from around the alignmentfeatures prior to wafer imaging. Both of these approaches, however, aretime consuming and can reduce the amount of space on a wafer availablefor producing dies. Therefore, it would be desirable to have a systemfor imaging and cutting semiconductor wafers that have infraredinhibiting layers obscuring alignment features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a prior art semiconductor imaging andcutting system.

FIG. 2 is a schematic illustration of a semiconductor wafer imaging andcutting system in accordance with an embodiment of the invention.

FIG. 3 is a flow diagram illustrating a method for imaging and dicing asemiconductor wafer in accordance with an embodiment of the invention.

FIG. 4 is a schematic illustration of a semiconductor wafer imaging andcutting system in accordance with another embodiment of the invention.

FIG. 5 is a schematic diagram of a wafer X-ray image in accordance withan embodiment of the invention.

FIG. 6 is a schematic diagram of a microelectronic device substrate thatincludes a plurality of variable-pitch microelectronic devices inaccordance with an embodiment of the invention.

FIG. 7 is a schematic block diagram of an apparatus for singulatingsemiconductor workpieces in accordance with an embodiment of theinvention.

FIG. 8 is a flow diagram illustrating a process for singulating dies ofa semiconductor workpiece in accordance with an embodiment of theinvention.

FIG. 9 is a schematic plan view of a semiconductor workpiece having diespositioned in accordance with an embodiment of the invention.

FIG. 10 is an enlarged plan view illustrating a portion of thesemiconductor workpiece shown in FIG. 9.

FIG. 11 is a plan view illustrating irregularly spaced dies of anindividual semiconductor workpiece, along with representative dicingcuts made in accordance with embodiments of the invention.

FIG. 12 illustrates a semiconductor workpiece having vacancies, andassociated singulation cuts made in accordance with embodiments of theinvention.

FIG. 13 illustrates a portion of a semiconductor workpiece havingdefective dies, and associated singulation cuts made in accordance withan embodiment of the invention.

FIGS. 14A and 14B illustrate portions of a semiconductor workpiece thatmay move relative to each other during a dicing operation in accordancewith an embodiment of the invention.

FIG. 15 illustrates a cracked semiconductor workpiece, along with dicingcuts made in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

The following disclosure describes methods and systems for imaging anddicing semiconductor wafers and other microelectronic device substrates.Specific details of several embodiments of the disclosure are describedbelow with reference to semiconductor workpieces (“workpieces”) andsystems for processing the workpieces. The workpieces can includemicromechanical components, data storage elements, optics, read/writecomponents and/or other features. For example, the workpieces caninclude wafers having dies, including SRAM, DRAM (e.g., DDR-SDRAM),flash-memory (e.g., NAND flash-memory), processor, imager, and/or otherdies. Substrates can be semiconductive pieces (e.g., doped siliconwafers, gallium arsenide wafers, or other semiconductor wafers),non-conductive pieces (e.g., various ceramic substrates), or conductivepieces. Several other embodiments of the invention can haveconfigurations, components, or procedures different than those describedin this section. A person of ordinary skill in the art, therefore, willaccordingly understand that the invention may have other embodimentswith additional elements, or the invention may have other embodimentswithout several of the elements shown and described below with referenceto FIGS. 2-15.

Many specific details of certain embodiments of the invention are setforth in the following description and in FIGS. 2-15 to provide athorough understanding of these embodiments. A person skilled in theart, however, will understand that the invention may be practicedwithout several of the details described below, or with additionaldetails which can be added to the invention. Well-known structures andfunctions often associated with semiconductor wafers, associated imagingand cutting systems, and microelectronic devices in general have notbeen shown or described in detail to avoid unnecessarily obscuring thedescription of the various embodiments of the invention. Where thecontext permits, singular or plural terms may also include plural orsingular terms, respectively. Moreover, unless the word “or” isexpressly limited to mean only a single item exclusive from the otheritems in reference to a list of two or more items, then the use of “or”in such a list means including (a) any single item in the list, (b) allof the items in the list, or (c) any combination of the items in thelist. Additionally, the term “comprising” is used throughout thefollowing disclosure to mean including at least the recited feature(s)such that any greater number of the same feature and/or additional typesof features or components is not precluded.

While various aspects of the invention are described below in thecontext of semiconductor wafers, those of ordinary skill in the art willunderstand that the methods and systems described herein can also beused to singulate dies and/or other microelectronic devices from othertypes of substrates. For example, the various methods and systemsdescribed herein can also be used to separate individual dies from a BUPsubstrate.

A particular method for singulating semiconductor dies includesdetecting spacing information for irregularly spaced dies of anindividual semiconductor workpiece, and, based at least in part on thespacing information, automatically controlling a process for singulatingthe dies of the individual semiconductor workpiece. In furtherparticular arrangements, the method can include directing a cutter(e.g., a laser beam or water jet) to deviate from a single straight linepath as it traverses a semiconductor workpiece. Further details of theseand other methods and associated systems are discussed below.

FIG. 2 is a schematic illustration of a semiconductor wafer imaging andcutting system 200 (“cutting system 200”) in accordance with anembodiment of the invention. As described in greater detail below, thecutting system 200 includes an X-ray imaging system (e.g., afluoroscopic X-ray imaging system) for aligning a semiconductor wafer202 (“wafer 202”) for dicing. The wafer 202 can include various types ofmicroelectronic devices (e.g., DRAM, SRAM, Flash, Imagers, PCRAM, MRAM,etc.) which are not shown in FIG. 2. The wafer 202 can also include aninfrared inhibiting layer 203 applied to a backside 218. The infraredinhibiting layer 203 extends over all or a portion of the backside 218such that it covers all, or at least a substantial portion, of the waferalignment features (not shown in FIG. 2). The infrared inhibiting layer203 can include a metal layer (e.g., an aluminum, copper, tungsten,nickel layer, etc.) to reduce electromagnetic interference (EMI), shieldagainst infrared radiation and/or for other purposes. The infraredinhibiting layer 203 can also include quartz, mold compound, and/orother compounds and materials known in the art that obscure infraredimaging of wafer alignment features.

The wafer 202 is carried by a wafer holder 204 (e.g., a chuck, such as avacuum chuck). To facilitate imaging and/or cutting, the wafer holder204 can rotate in a θ direction and move laterally in an X direction. Inother embodiments, the wafer holder 204 can also move up and down in a Ydirection or back and forth in a Z direction.

The cutting system 200 further includes a low intensity X-ray emitter orsource 222 operably mounted to a dicing machine 214. The X-ray source222 projects an X-ray beam 226 through the wafer 202 and onto a detector224 a (e.g., a detector screen, such as a flat panel detector screen, afluorescent screen, a Cesium iodide (CsL) screen, etc.). Although thedetector 224 a is positioned proximate to a lower portion of the waferholder 204 in the illustrated embodiment, in other embodiments, thecutting system 200 can include other detector screens in other positionsbeneath the wafer 202. For example, the cutting system 200 can include asecond detector screen 224 b on an opposite side of the wafer holder204, and/or a third detector screen 224 c which is incorporated into thewafer holder 204. The cutting system 200 can be positioned within ashielded enclosure 230 to contain the X-ray radiation from the X-raysource 222.

The detector 224 a provides wafer image information to a signalprocessor or computer 212. The detector 224 a can optionally be coupledto an image intensifier 228 that intensifies the wafer image beforetransmitting the image information to the computer 212. As described ingreater detail below, the wafer image information is processed by thecomputer 212 to determine the relative locations of alignment featureson the wafer 202. This information is then converted into instructionsfor controlling the dicing machine 214 during cutting of thesemiconductor wafer 202.

The dicing machine 214 can include a cutter device 216 for cutting thesemiconductor wafer 202 and/or singulating the dies and/or othermicroelectronic devices on the wafer. In the illustrated embodiment, thecutter device 216 can include a saw having, for example, adiamond-tipped blade. In other embodiments, the cutter device 216 caninclude a water jet cutting device, a laser cutting device, and/or othersuitable wafer cutting devices known in the art.

FIG. 3 is a flow diagram illustrating a method 300 of imaging and dicinga semiconductor wafer or other microelectronic device substrate inaccordance with an embodiment of the invention. For purposes ofillustration, the method 300 is described below with reference to thecutting system 200 of FIG. 2. In block 302, the wafer 202 is positionedon the wafer holder 204 between the X-ray source 222 and the detector224 a. In block 304, the X-ray source 222 emits the X-ray beam 226through the wafer 202 and the infrared inhibiting layer 203. The X-raysource 222 and/or the wafer holder 204 can be moved as necessary to atleast generally align the X-ray beam 226 with an alignment feature (notshown in FIG. 2, but described in detail below with reference to FIG. 5)in the wafer 202. In block 306, the detector 224 a detects at least aportion of the X-rays passing through the wafer 202. X-ray imageinformation is then transmitted from the detector 224 a to the computer212. In block 308, the computer 212 generates wafer alignmentinformation based at least in part on the X-ray image informationreceived from the detector 224 a. In block 310, the computer 212transmits the wafer alignment information (in, e.g., the form of cuttinginstructions) to the dicing machine 214. In block 312, the dicingmachine 214 operates the cutter device 216 to singulate the dies on thewafer 202. After block 312, the routine ends.

FIG. 4 is a schematic illustration of a semiconductor imaging andcutting system 400 (“cutting system 400”) in accordance with anotherembodiment of the invention. Many features of the cutting system 400 areat least generally similar in structure and function to thecorresponding features of the cutting system 200 described above withreference to FIGS. 2 and 3. For example, the cutting system 400 includesa movable wafer holder 404 that supports a semiconductor wafer 402. Inthis particular embodiment, however, the cutting system 400 furtherincludes an X-ray source 422 that is spaced apart from a dicing machine414.

To use the cutting system 400, the wafer holder 404 starts in a firstposition 431 so that a detector screen 424 can obtain an X-ray image ofthe wafer 402. In the illustrated embodiment, the detector screen 424 ismounted independently of the wafer holder 404 in alignment with theX-ray source 422. In other embodiments, the detector screen 424 can beattached or otherwise incorporated into the wafer holder 404 asdescribed above with reference to FIG. 2. After the wafer 402 has beensuitably imaged in the first position 431, the wafer holder 404 moves toa second position 432 proximate to the dicing machine 414. The dicingmachine 414 then cuts the wafer 402 based at least in part on the X-rayimage information received from the detector screen 424.

FIG. 5 is a schematic diagram illustrating an X-ray image 540 of thesemiconductor wafer 202 captured by the detector 224 a in accordancewith an embodiment of the invention. In this embodiment, thesemiconductor wafer 202 includes a plurality of fiducials or alignmentfeatures 542 (identified individually as a first alignment feature 542a, a second alignment feature 542 b, and a third alignment feature 542c). The alignment features 542 can include metals and/or other materialsthat are X-ray opaque, and thus can be identified by X-ray imaging.

To align the semiconductor wafer 202 for cutting, the X-ray image 540 istaken of a portion of the semiconductor wafer 202 that includes, forexample, the second alignment feature 542 b. X-ray image data from thedetector 224 a is then transmitted to the computer 212 (FIG. 2) so thatany offset of the second alignment feature 542 b (shown by a firstdistance D1 and a second distance D2) relative to a known datum 544 canbe determined. In one embodiment, the known datum 544 can represent theposition the second alignment feature 542 b would be in if thesemiconductor wafer 202 was properly aligned with the dicing machine214. Once the extent of any offset is known, the computer 212 can adjustthe position of the dicing machine 214 as necessary to account for anymisalignment of the semiconductor wafer 202. In certain embodiments, itmay be desirable to determine the position of two or more of thealignment features 542 in the foregoing manner to enhance the level ofwafer alignment prior to dicing.

FIG. 6 is a schematic diagram of a microelectronic device substrate 602having a plurality of variable-pitch microelectronic devices 650(identified individually as microelectronic devices 650 a-i) inaccordance with another embodiment of the invention. The microelectronicdevices 650 can include, for example, BUP devices held together in thesubstrate 602 by a fill material (e.g., mold compound) 652. As is oftenthe case with BUP device substrates, the spacing between the devices 650can vary. As a result, cutter street widths (or “kerfs”) can vary from arelatively narrow street width 661 to a relatively wide street width662. Furthermore, one or more of the individual devices 650 may also beskewed relative to the other microelectronic devices, as illustrated bythe microelectronic device 650 e. When singulating the microelectronicdevices 650 from the substrate 602, however, it is desirable to have thesame amount of mold compound surrounding each of the individual devices650 following the singulation process, as illustrated by the phantomlines extending around the microelectronic devices 650 e-650 h.

Because some of the microelectronic devices 650 (e.g., themicroelectronic device 650 e) may be skewed, a rotary saw blade may notbe able to negotiate the cutting path between two or more of thedevices. To address this problem, various embodiments of the inventioncan include a laser-based or high pressure water-based cutting device tocut around the individual microelectronic devices 650 and separate themfrom the substrate 602. (If a water jet cutting device is used to cutaround the individual microelectronic devices 650, then each of thedevices 650 may need to be individually supported in a manner known inthe art.) Some cutting devices (e.g., saws) have to make two or morepasses on a given street to achieve the desired street width and/orprovide the desired package size. However, if a laser cutting device isused, the spot size of the laser could be dynamically adjusted to varythe thickness of the cutting path. Similarly, if a water jet cuttingdevice is used, the jet stream diameter could be dynamically adjusted toprovide the desired cutting path width.

In one embodiment, the X-ray imaging and cutting system 200 describedabove with reference to FIGS. 2-5 can be used to singulate theindividual microelectronic devices 650 from the substrate 602 and leavea relatively even amount of mold material or “edge distance” around eachof the devices. In this embodiment, the cutting device 216 can includeeither a laser cutting device or a water jet cutting device that is ableto cut around the periphery of each of the individual devices 650. Tosingulate, for example, the microelectronic device 650 i, the cuttingsystem 200 takes a real-time X-ray image of alignment features 644 a-dto determine the actual location of the device 650 i before instructingthe dicing machine 214 to cut around the device. In another embodiment,the cutting system 200 can take an X-ray image that locates the edges ofthe device 650 i, and then instruct the dicing machine 214 to cut aroundthe device. In a further embodiment, the cutting system 200 can useX-ray information relating to the location of one or more contacts 654(e.g., bond-pads, solder balls, etc.) on the device 650 i.

While the use of an X-ray imaging system may be necessary in those caseswhere the semiconductor wafer or other microelectronic device substrateincludes a metal layer, the method disclosed herein of using laser-basedor water jet-based cutting devices to cut around variable pitchmicroelectronic devices is not limited to use with X-ray imagingsystems. Indeed, the cutting techniques disclosed herein can be employedwith many other types of alignment systems (e.g., visual, infrared,etc.) as long as the particular alignment system is able to locate theperiphery of the individual microelectronic devices.

FIG. 7 is a schematic block diagram of an apparatus 700 for singulatinga semiconductor workpiece 710 in accordance with several embodiments ofthe invention. The apparatus 700 can include a support 701 that carriesthe semiconductor workpiece 710 during one or more operations, adetection device 702 that detects characteristics of the semiconductorworkpiece 710, a singulation device 703 that singulates dies from thesemiconductor workpiece 710, and a controller 705 that directs theoperation of the foregoing components. The detection device 702, thesingulation device 703, and/or the support 701 can translate relative toeach other along x, y, and/or z axes, and can also rotate (e.g., aboutthe z axis) to position any of the components relative to the other.Characteristics of these components are described generally below, andassociated methods and techniques are then described in further detailwith reference to FIGS. 8-15.

The detection device 702 can be configured and positioned to detectselected characteristics of the semiconductor workpiece 710, includingbut not limited to information corresponding to the spacings betweenindividual dies or groups of dies of the semiconductor workpiece 710.Accordingly, the detection device 702 can include a vision system, forexample, a still camera or a motion camera. In a particular embodiment,the detection device 702 includes a camera that detects radiation in thevisible spectrum, and in other embodiments, the detection device 702 candetect radiation at other wavelengths, for example, infrared radiationor X-ray radiation. Representative embodiments of such detection deviceswere described above with reference to FIGS. 2-4. In any of theseembodiments, the apparatus 700 can include an appropriate illuminationsystem which may or may not be incorporated into the detection device702. For example, if the detection device 702 includes a visiblewavelength camera, the apparatus 700 can include a visible wavelengthillumination device. If the detection device 702 includes an X-raycamera, the apparatus 700 can include an appropriately positioned X-rayradiation source. In other embodiments, the detection device 702 canobtain information using other types of energy, for example, ultrasonicenergy.

In any of the foregoing embodiments, the controller 705 controls theactivation of the detection device 702, and optionally, the relativemotion between the detection device 702 and the support 701. Thedetection device 702 and the support 701 may move relative to each otherto allow the detection device 702 to obtain information over theentirety of the semiconductor workpiece 710, and/or to allow thedetection device 702 to provide detailed information for particularportions of the workpiece 710. This function can also be provided byequipping the detection device 702 with a zoom feature. The support 701can also move relative to the detection device 702 during thesingulation process, which is described below.

Based at least in part on the information received from the detectiondevice 702, the controller 705 controls the operation of the singulationdevice 703 so as to singulate dies from the semiconductor workpiece 710in a manner that accounts for spacing (and/or other) informationspecific to the particular semiconductor workpiece 710 presently at theapparatus 700. Accordingly, the controller 705 can include a computerreadable medium containing instructions (e.g., programmed instructions)that reduce or otherwise handle the data obtained from the detectiondevice 702, and direct the singulation device 703 accordingly. Thesingulation device 703 can include a cutter 704 positioned proximate tothe workpiece support 701 for singulating dies from the semiconductorworkpiece 710. In particular embodiments, the cutter 704 can include alaser (e.g., a hot laser or another type of laser), a liquid or gaseousjet (e.g., an abrasive or non-abrasive water jet) and/or other devices.In many arrangements, the cutter 704 does not include a rotary blade, soas to enable the cutter 704 to readily and precisely adjust the cuttingpath to account for irregular spacings between dies of the semiconductorworkpiece 710. However, in at least some arrangements, the cutter 704can include a rotary blade, for example, in situations in which thestraight line cuts made by such blades may be oriented to account forthe irregularities in die spacing. Further details of such arrangementswill be described later with reference to FIGS. 11-15.

The apparatus 700 shown in FIG. 7 illustrates a detection device 702 anda singulation device 703 that operate on the semiconductor workpiece 710while it is at a single station. This arrangement can reduce the needfor repositioning the workpiece 710 after the characteristics of theworkpiece 710 have been detected and before the workpiece 710 issingulated in accordance with the detected characteristics. Such anarrangement can reduce the likelihood that the workpiece 710 will becomemisaligned between the detection operation and the singulationoperation. However, in other embodiments, for example, when thealignment of the workpiece 710 can be precisely controlled or accountedfor when the workpiece 710 is moved, the detection device 702 and thesingulation device 703 can be located at different stations.

FIG. 8 illustrates a representative process 750 for singulating diesfrom a semiconductor workpiece 710 in accordance with severalembodiments of the invention. The process 750 can include detectingspacing information for irregularly spaced dies of an individualsemiconductor workpiece (process portion 752). Based at least in part onthe spacing information, the process 750 can further includeautomatically controlling a process for singulating the dies of theindividual semiconductor workpiece (process portion 754). The dies canbe singulated using one or more of several techniques to account for theirregular spacing of the dies. For purposes of illustration, severaldifferent techniques are shown together in FIG. 8, but it will beunderstood by one of ordinary skill in the relevant art that any onetechnique or any combination of techniques may be used for a givenworkpiece. These techniques include, but are not limited to, directing acutter along a path that deviates from a straight line (process portion756). Process portion 758 includes making multiple passes along a singlestreet positioned between rows or columns of dies. In process portion760, the width of a kerf made by the cutter can be changed. In otherprocesses, individual dies can be separated from the workpiece (processportion 762), and in still further processes, individual dies can beavoided, for example, if such dies are inoperable or defective (processportion 764). Specific locations of the workpiece (e.g., vacancies ofthe workpiece where no die exists) can also be avoided with thistechnique.

In process portion 770, it is determined whether or not to update thespacing information obtained in process portion 752. For example, insome instances, making a cut between dies of the workpiece can cause thedies to shift, changing the relative spacing between such dies. In suchcases, it may be desirable to update the spacing information, and soprocess portion 752 is repeated. If the information need not be updated,then in process portion 772 it is determined whether all the diestargeted for singulation have been singulated. If they have not, theprocess returns to process portion 754. If they have, the process ends.

FIG. 9 is a schematic plan view of the workpiece 710 prior to undergoinga singulation operation in accordance with an embodiment of theinvention. The workpiece 710 can include a wafer or other collection ofdies 711 that are to be singulated. For example, the workpiece 710 caninclude a collection of dies that have already been singulated from awafer, then repositioned or repopulated on a substrate, and thenencapsulated. The workpiece 710 is generally supported on a film frame730. The film frame 730 includes a frame 732 carrying a film 731, whichin turn is adhesively attached to the semiconductor workpiece 710 tosupport the workpiece 710 during the singulation operation. Typically,the same film frame 730 also supports the semiconductor workpiece 710during the detection operation so that the semiconductor workpiece 710retains the same orientation relative to the film frame 730 during boththe detection operation and the singulation operation. In otherembodiments, this need not be the case, and in still furtherembodiments, the workpiece 710 can be supported by devices other thanthe film frame 730, or the workpiece 710 can be unsupported.

FIG. 10 is a plan view of a portion of a representative workpiece 710having spaced apart dies 711. The illustrated workpiece 710 is coveredwith an encapsulant 714, though in other cases, the workpiece 710 is notencapsulated. Each of the dies 711 includes die edges 713 which areshown in dashed lines in FIG. 10 as result of the overlying encapsulant714. The dies 711 can also include conductive couplers 715, for example,solder balls that project through the encapsulant 714. In otherembodiments, the conductive couplers 715 can include other structures(e.g., solder bumps, bumps made from other conductive materials, or wirebonds). In many cases, the conductive couplers 715 and/or the die edges713 can be detected by the detector 702 (FIG. 7) and can provide enoughinformation to enable the dies 711 to be accurately singulated, despitebeing irregularly spaced. For example, if the workpiece 710 isencapsulated, the detection device 702 can detect the location andorientation of individual dies 711 by detecting the conductive couplers715 using visible light. Alternatively, the detection device 702 candetect the die edges 713 using X-ray radiation or another radiation towhich the encapsulant 714 is transparent. If the workpiece 710 has noencapsulant 714, then the detection device 702 can use visible light todetect the die edges 713.

In some cases, the dies 711 may have other features which arespecifically included to provide spacing information. For example, thedies 711 can include fiducials 716 that extend through the encapsulant714. For purposes of illustration, two fiducials 716 are shown for eachdie in FIG. 10, but it will be understood that in other embodiments, asingle fiducial 716 or more than two fiducials 716 may be used toprovide a basis for the detected spacing information. The fiducials 716(or other features) may be used in addition to or in lieu of theconductive couplers 715 and/or the die edges 713 to provide spacinginformation.

In any of the foregoing embodiments, neighboring dies 711 andneighboring groups of dies 711 are separated by streets 712. Each streethas a street width W. In general, the streets W are of uniform width andspacing, or otherwise follow a uniform pattern. However, as will bediscussed in greater detail below with reference to FIGS. 11-15, in somecases the spacings are not uniform. Aspects of the present invention aredirected to accurately singulating the dies even when the spacingsbetween dies 711 are not uniform. For purposes of illustration, theworkpieces shown in FIGS. 11-15 are shown without an encapsulant;however, it will be understood that some or all of the operationsdescribed in connection with these Figures may be performed onworkpieces with or without an encapsulant.

FIG. 11 illustrates a portion of a workpiece 710 having dies 711 thatare irregularly spaced. At least some of the features of the workpiece710 may be generally similar to corresponding features of the substrate602 described above with reference to FIG. 6, though the workpiece 710has additional features as well. For purposes of completeness, therelevant portions of the workpiece 710 (including some described abovewith reference to FIG. 6) are described with reference to FIG. 11. Forpurposes of illustration, several different types of spacingirregularities are shown together on the same workpiece 710 in FIG. 11.It will be understood that in many cases, the same workpiece 710 willnot have all these irregularities, while in other cases, the workpieces710 may have more and/or different irregularities than are shown in FIG.11.

The dies 711 are arranged in rows 722 and columns 717, including first,second, third, fourth and fifth columns 717 a, 717 b, 717 c, 717 d, and717 e respectively. The first and second columns 717 a, 717 b areseparated by a first street 712 a, and the second and third columns 717b, 717 c are separated by a second street 712 b. In the illustratedembodiment, the first street 712 a has the “correct” (e.g., specified)street width W1, while the second street 712 b has an incorrect (e.g.,too large) street width W2. Accordingly, the pitch between the dies canvary from one part of the workpiece to another. When the first column717 a is singulated from the second column 717 b, the cutter creates afirst kerf 718 a. The offset O between the dies 711 in the first column717 a and the edge of the first kerf 718 a, and the dies 711 of thesecond column 717 b and the edge of the first kerf 718 a are the sameand have the correct (e.g., specified) value. However, if the same kerfwere to be made between the second and third columns 717 b, 717 c, theoffset between the kerf and the dies 711 of one or both of the columns717 b, 717 c would be too large. Accordingly, the dies 711 of the secondand third columns 717 b, 717 c are specifically singulated to accountfor this irregularity. In a particular embodiment, two kerfs (shown as asecond kerf 718 b and a third kerf 718 c) are made in the same street(e.g., the second street 712 b). As a result, the offset O between thedies 711 of the second column 717 b and the second kerf 718 b is thesame as the offset O between dies 711 of the third column 717 c and thethird kerf 718 c.

In another arrangement, a single kerf can be made between the secondcolumn 717 b and the third column 717 c, but it can have a greater widththan that of the first kerf 718 a. For example, if the kerf is made witha water jet or a laser beam, the diameter of the water jet or the laserbeam can be increased to ablate or otherwise remove additional materialfrom between the second and third columns 717 b, 717 c. FIG. 11illustrates a fourth (wider) kerf 718 d, identified by a circle thatrepresents the diameter of a jet or beam. When traversed along thesecond street 712 b, the jet or beam ablates material to form a singlewide kerf 718 d. Accordingly, the fourth kerf 718 d produces the samedesired offset O between its edges and the edges of dies 711 in both thesecond column 717 b and the third column 717 c. If the fourth kerf 718 dis made with a rotating blade, the blade can have a different width thanthat of the blade used to make the first kerf 718 a, so as to accountfor the increased spacing between the second and third columns 717 b,717 c, relative to the spacing between the first and second columns 717a, 717 b.

In other embodiments, the spacing irregularity can produce an angularoffset. For example, as shown in FIG. 11, the third row 717 c includes asingle misaligned die 711 c that is angularly offset relative to itsneighbors. If the workpiece 710 were cut using standard methods, it isquite likely that the misaligned die 711 c would be cut into andtherefore not usable. However in a particular embodiment, the individualdie 711 c can be singulated from the workpiece 710 separately from theother dies 711, as indicated by a fifth kerf 718 e. In this particulararrangement, the fifth kerf 718 e includes a cut or series of cuts thatcompletely encircle the misaligned die 711 c so it can be removed fromthe workpiece 710. The remaining dies 711 on the workpiece 710 can thenbe singulated using a succession of vertical cuts followed by horizontalcuts, without cutting into or through the misaligned die 711 c.

In still another embodiment, an entire column or portion of a column ofdies can be angularly offset from its neighbors. For example, the fourthcolumn 717 d of dies 711 is rotated relative to the y axis by anon-zero, non-orthogonal angle θ so that a corresponding third street712 c between the third column 717 c and the fourth column 717 d has avariable width. Two representative widths are indicated as W3 and W4.One approach to accounting for the variable street width is to providetwo kerfs, e.g., a sixth kerf 718 f aligned along the third column 717 cand a seventh kerf 718 g aligned along the fourth column 717 d, in amanner generally similar to that described above with reference to thesecond and third kerfs 718 b, 718 c, but with the sixth and seventhkerfs 718 f, 718 g being nonparallel. Another approach is to change thewidth of a single kerf 718 h (represented by circles) as the kerf 718 hextends in the y direction. For example, if the kerf 718 h is made witha laser beam or water jet, the diameter of the laser beam or water jetcan be increased as the kerf 718 h progresses in the y direction toaccount for the increasing width of the third street 712 c.

In yet another embodiment, a given row or column of dies may have anirregularity along the length of the row or column. For example, thefifth column 717 e of dies 711 can include an offset or “joggle”part-way along the column. Accordingly, an associated process caninclude cutting a kerf 718 i that follows a path deviating from a singlestraight line along the length of the fifth column 717 e. In one aspectof this embodiment, the kerf 718 i can be formed from a series ofstraight line kerfs that account for the offset in the dies 711. Inanother embodiment, the fifth column 717 e can be singulated with acurved kerf 718 j to account for the offset in the dies 711.

FIG. 12 is a partially schematic, top plan view of a workpiece 710having dies 711 that are irregularly spaced as a result of vacancies 719positioned between at least some of the dies 711. In some cases, it maybe desirable to account for the vacancies 719 by cutting them out (asindicated by first kerfs 1218 a) and then proceeding with singulatingthe remaining dies 711 with a series of cuts parallel to the y axis,followed by a series of cuts parallel to the x axis. In otherembodiments, it may be desirable to separate individual dies 711 fromthe workpiece 710, without singulating the vacancies 719. Such anarrangement is illustrated by second kerfs 1218 b positioned aroundindividual dies 711. In other still further embodiments, the twoforegoing techniques may both be used on a single workpiece, for examplea workpiece that has a preponderance of vacancies 719 in one area and apreponderance of dies 711 in another area.

FIG. 13 illustrates a technique used to singulate first dies 711 a(e.g., non-defective dies or “known good dies”), that are irregularlyspaced from each other by virtue of second dies 711 b (e.g., defective,inoperative, or “bad” dies). Depending on the relative number of firstdies 711 a and second dies 711 b, individual first dies 711 a may besingulated from the workpiece 710 and the rest of the workpiece 710discarded, or individual second dies 711 b may be singulated from theworkpiece 710, and the remaining first dies 711 a can be singulatedusing a series of cuts parallel to the y axis followed by a series ofcuts parallel to the x axis. The spacing information on which thesingulation process is conducted can in this case include the locationsof the first dies 711 a and/or the second dies 711 b.

FIG. 14A illustrates a portion of a workpiece 710 having dies 711 thatare initially uniformly spaced from each other in both the x and ydirections. Accordingly, the columns of dies 711 are separated by firststreets 712 a generally parallel to the y axis and having a width W1,and the rows of dies 711 are separated by series of second streets 712 bgenerally parallel to the x axis and having a width W2. The workpiece710 can include build-up packages (BUPs) or other arrangements ofsingulated dies 711 that are then encapsulated. Because the workpiece710 is carried by a film 721 that can be flexible, resilient, and/orstretchable, the relative positions of neighboring dies 711 may changeduring the course of a singulation process. For example, as shown inFIG. 14B a first kerf 1418 a has been cut along the first street 712 aand has caused the two neighboring columns of dies 711 to move apartfrom each other in the x direction, as indicated by arrow S1. After asecond kerf 1418 b has been made along one of the second streets 712 b,the dies 711 can again move apart, this time in the y direction, asindicated by arrow S2. As a result, the relative spacing betweenneighboring dies 711 may change during the dicing process. If thischange is not accounted for, it can result in subsequent kerfs beingmisaligned or mispositioned. To account for this shift, the detectiondevice 702 (FIG. 7) can be operated at one or more times during thecourse of a singulation operation. For example, the detection device 702can be operated on a continuous basis, or after each street is cut. In aparticular embodiment, the information obtained via the detection device702 can be used real time or nearly real time to update the spacinginformation for each die 711 before it is cut and/or while it is beingcut. In this way, misalignments that may result from individual dies 711or groups of dies 711 being separated from the workpiece may beaccounted for and corrected as the singulation process continues.

FIG. 15 schematically illustrates still another instance in which dies711 may be irregularly spaced from each other. In one aspect of thisarrangement, the workpiece 710 has a crack 721 that causes a firstcolumn 717 a of dies 711 to be misaligned angularly relative to a secondcolumn 717 b. As is also shown in FIG. 15, one of the dies 711 astraddles the crack 721 and is itself cracked. One or more of any of theforegoing techniques may be used to account for this irregularity. Forexample, the cracked die 711 a may be removed from the rest of theworkpiece 710 as single die, and the rest of the dies 711 thensingulated. The rest of the dies 711 may be singulated by providing afirst kerf 1518 a that is parallel to the first column 717 a, and asecond kerf 1518 b that is parallel to the second column 717 b.Alternatively, a single kerf having a varying kerf width can be madebetween the two rows to account for the angular offset between the tworows.

Features of several of the foregoing embodiments can improve the processin accordance with which semiconductor workpieces are singulated. Forexample, aspects of the foregoing processes allow greater utilization ofworkpieces having irregularly spaced dies, which otherwise may becomedamaged and/or may be discarded during the course of processing. Thisarrangement can improve the efficiency with which the foregoingprocesses are conducted by improving the yield of dies produced by theprocesses.

Another feature of at least some of the foregoing embodiments is thatthey can be used to produce dies having more uniform dimensions becauseeach cut can be made based on information specific to the region that isbeing cut, rather than being based on information generic tosemiconductor workpieces of a particular type. The more uniform dies aremore likely to meet quality control specifications, and again result ina greater yield for a given workpiece. This arrangement can also allowthe dies to be made smaller because the manufacturer need not accountfor likely misalignments by oversizing the offset O around the edges ofpackaged dies.

In many cases, the cutter used to make the foregoing kerfs includes alaser, water jet, or other device that can be programmed to follow anypath, including straight line or curved paths. In other embodiments, atleast some of the techniques described above can be performed by blades.For example, making multiple kerfs along a single street can beperformed with a blade, when the cuts are straight. Making multiple cutshaving different kerf widths can be made by changing the thickness ofthe blade from one cut to another. Making cuts at a non-zero angle θrelative to the x or y axis can be made by rotating the cutter or theworkpiece by the proper amount.

Yet a further feature of at least some of the foregoing embodiments isthat the workpiece can be singulated without rotating either the cutteror the workpiece. For example, when the cutter includes a water jet or alaser beam, the water jet or laser beam can be moved over the surface ofthe workpiece to singulate dies having any of a wide variety oforientations by simply positioning the jet or beam, without rotating theworkpiece or the cutter. This is unlike existing arrangements in whichthe workpiece has one orientation while singulating cuts are madebetween columns of dies, and is then rotated by 90° for cuts madebetween neighboring rows. By eliminating the need to rotate the cutteror the workpiece, the overall apparatus can be made simpler, as itrequires fewer moving parts.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theinvention. For example, the workpieces and dies may have configurationsand/or irregularities other than those shown in the Figures. Theworkpieces may be supported by devices other than film frames, and maybe encapsulated, partially encapsulated, or not encapsulated at all.Certain aspects of the invention described in the context of particularembodiments may be combined or eliminated in other embodiments. Forexample, any given workpiece may have any one of the irregularitiesdescribed above, or any combination of such irregularities. Further,while advantages of associated with certain embodiments of the inventionhave been described in the context of those embodiments, otherembodiments may also exhibit such advantages, and not all embodimentsneed necessarily exhibit such advantages to fall within the scope of theinvention. Accordingly, the invention is not limited except as by theappended claims.

I/We claim:
 1. An apparatus for singulating semiconductor dies,comprising: a detection device having a semiconductor workpiece supportand a detector positioned proximate to the support, the detector beingpositioned to receive a signal corresponding to a location ofirregularly spaced dies of the workpiece; a singulation device; and acontroller operatively coupled to the detection device and thesingulation device, the controller having instructions directingrelative motion between the singulation device and the workpiece supportbased at least in part on information received from the detectorcorresponding to the location of the irregularly spaced dies of theworkpiece.
 2. The apparatus of claim 1 wherein the singulation deviceincludes a blade cutter.
 3. The apparatus of claim 1 wherein thesingulation device and the workpiece support are not rotatable relativeto each other.
 4. The apparatus of claim 1 wherein the controller hasinstructions directing a change in a width of a kerf made by thesingulation device, based at least in part on information received fromthe detector.
 5. The apparatus of claim 1 wherein the controller hasinstructions directing the singulation device to make multiple cutsalong a single street, based at least in part on information receivedfrom the detector.
 6. The apparatus of claim 1 wherein the controllerhas instructions directing the singulation device to make a first cutand a second cut oriented at a non-zero, non-orthogonal angle relativeto the first cut.